Drug interactions
Fosphenytoin + Lacosamide
Severity: Moderate
Fosphenytoin and Lacosamide: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Phenytoin derived from fosphenytoin is an enzyme inducer and may modestly lower lacosamide exposure. Both drugs slow cardiac conduction through sodium-channel effects, so AV block and bradyarrhythmias are possible.
What this interaction means in plain words
Fosphenytoin and Lacosamide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fosphenytoin belongs to Central Nervous System; Lacosamide belongs to Central Nervous System.
Why it happens
Enzyme induction by phenytoin increases lacosamide clearance, with additive sodium-channel blockade on cardiac conduction.
What to do
Check ECG before and after lacosamide titration, especially in patients with conduction disease or cardiac disease. Monitor seizure control and adjust lacosamide as needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Lacosamide
- Lacosamide + Zuranolone Major
- Atazanavir + Lacosamide Moderate
- Carbamazepine + Lacosamide Moderate
- Cenobamate + Lacosamide Moderate
- Clarithromycin + Lacosamide Moderate
- Daridorexant + Lacosamide Moderate
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Lacosamide?
MediHelp rates the interaction as moderate. Fosphenytoin and Lacosamide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin derived from fosphenytoin is an enzyme inducer and may modestly lower lacosamide exposure. Both drugs slow cardiac conduction through sodium-channel effects, so AV block and bradyarrhythmias are possible.
How serious is the interaction between Fosphenytoin and Lacosamide?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check ECG before and after lacosamide titration, especially in patients with conduction disease or cardiac disease. Monitor seizure control and adjust lacosamide as needed.
What other medicines interact with Lacosamide?
MediHelp also lists interactions of Lacosamide with, for example, Zuranolone, Atazanavir, Carbamazepine. The full list is on the Lacosamide page.
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